Mr Lidington has been tasked with “hand holding” the Irish boss Leo Varadkar and Foreign Minister Simon Coveney through the final phases of negotiations, but Brexiteers believe he is using the role to push a softer agenda than the Exit Secretary.

They point to a change in tone from the Dublin for Britain being able to stay in a customs union as part of the controversial “backstop” plan.

The Sun understands tensions came to a head last week when Mr Lidington travelled to Dublin for meetings, while Mr Raab was dispatched to Northern Ireland.

At the time Downing Street stressed the excellent relations Mr Lidington had with the Irish bosses, who he is said to be in constant contact with via text message.